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Appl. Sci., Volume 11, Issue 3 (February-1 2021) – 462 articles

Cover Story (view full-size image): Femtosecond pulsed lasers offer great advantages for contactless and, thus, gentle and wear-free manufacturing of optical elements with freely selectable geometry. Against this background, two lens arrays are fabricated for a compact beam homogenizer module by an all laser-based technology employing a precise femtosecond pulsed laser ablation and a CO2 laser polishing step. The fabricated elements are assembled together with a laser-cut aperture into an additively manufactured housing revealing a length of only 16 mm. The functionality of the final beam shaping module is tested by transferring an incoming intensity distribution into a high-quality Top-Hat. View this paper
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Article
Constructing More Complete Control Flow Graphs Utilizing Directed Gray-Box Fuzzing
Appl. Sci. 2021, 11(3), 1351; https://doi.org/10.3390/app11031351 - 02 Feb 2021
Viewed by 1134
Abstract
Control Flow Graphs (CFGs) provide fundamental data for many program analyses, such as malware analysis, vulnerability detection, code similarity analysis, etc. Existing techniques for constructing control flow graphs include static, dynamic, and hybrid analysis, which each having their own advantages and disadvantages. However, [...] Read more.
Control Flow Graphs (CFGs) provide fundamental data for many program analyses, such as malware analysis, vulnerability detection, code similarity analysis, etc. Existing techniques for constructing control flow graphs include static, dynamic, and hybrid analysis, which each having their own advantages and disadvantages. However, due to the difficulty of resolving indirect jump relations, the existing techniques are limited in completeness. In this paper, we propose a practical technique that applies static analysis and dynamic analysis to construct more complete control flow graphs. The main innovation of our approach is to adopt directed gray-box fuzzing (DGF) instead of coverage-based gray-box fuzzing (CGF) used in the existing approach to generate test cases that can exercise indirect jumps. We first employ a static analysis to construct the static CFGs without indirect jump relations. Then, we utilize directed gray-box fuzzing to generate test cases and resolve indirect jump relations by monitoring the execution traces of these test cases. Finally, we combine the static CFGs with indirect jump relations to construct more complete CFGs. In addition, we also propose an iterative feedback mechanism to further improve the completeness of CFGs. We have implemented our technique in a prototype and evaluated it through comparing with the existing approaches on eight benchmarks. The results show that our prototype can resolve more indirect jump relations and construct more complete CFGs than existing approaches. Full article
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Article
Application of Inverse Neural Networks for Optimal Pretension of Absorbable Mini Plate and Screw System
Appl. Sci. 2021, 11(3), 1350; https://doi.org/10.3390/app11031350 - 02 Feb 2021
Cited by 1 | Viewed by 737
Abstract
Mandibular fractures are common facial lesions typically treated with titanium plate and screw systems; nevertheless, this material is associated with secondary effects. Absorbable material for implants is an alternative to titanium, but there are also problems such as incomplete screw insertion and screw [...] Read more.
Mandibular fractures are common facial lesions typically treated with titanium plate and screw systems; nevertheless, this material is associated with secondary effects. Absorbable material for implants is an alternative to titanium, but there are also problems such as incomplete screw insertion and screw breakage due to high pretension in the screw caused by the insertion torque. The purpose of this paper is to find the optimal screw pretension (SP) in absorbable plate and screw systems by means of artificial neural network (ANN) and its inverse (ANNi). This optimal SP must satisfy a desired maximum von Mises strain (MVMS). For training the ANN, a database was generated by means of a design of experiments (DOE). Each DOE configuration was solved by means of finite element method (FEM) calculations. To obtain the optimal value for (SP) in the mini absorbable screw for fracture fixation, a strategy to invert the ANN is developed. Using the ANN coefficients, a sensitive study was performed to identify the influence of the design parameters in the MVMS. The optimal SP obtained was 14.9742 N. The MVMS condition was satisfied with an error less than 1.1% in comparison with FEM and ANN results. The screw shaft length is the most influencing MVMS parameter. Full article
(This article belongs to the Section Applied Biosciences and Bioengineering)
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Article
Deciphering the Antitussive, Expectorant, and Anti-Inflammatory Potentials of ShashamKyeongok-Go and Their Phytochemical Attributes: In Vivo Appraisal in ICR Mice
Appl. Sci. 2021, 11(3), 1349; https://doi.org/10.3390/app11031349 - 02 Feb 2021
Viewed by 968
Abstract
In this paper, we hypothesized that ShashamKyeongok-go (SKOG) is a mixed preparation of Adenophorae Radix powder (AR) and Kyeongok-go (KOG). SKOG may be served as a novel preventive and/or therapeutic agent for various respiratory diseases. SKOG were orally administered to ICR mice at [...] Read more.
In this paper, we hypothesized that ShashamKyeongok-go (SKOG) is a mixed preparation of Adenophorae Radix powder (AR) and Kyeongok-go (KOG). SKOG may be served as a novel preventive and/or therapeutic agent for various respiratory diseases. SKOG were orally administered to ICR mice at 400, 200, and 100 mg/kg once a day for 11 days to examine antitussive, expectorant, and anti-inflammatory effects. The NH4OH exposure-induced allergic acute inflammation with coughing responses was dose-dependently and significantly (p < 0.01) inhibited by pretreatment with SKOG at doses of 400, 200, and 100 mg/kg. With these concentrations of SKOG, the thickness of intrapulmonary secondary bronchus mucosa and the number of periodic acid Schiff stain-positive mucous-producing cells were significantly (p < 0.05 or p < 0.01) increased, as a result of the increased amount of phenol red secretion. Subsequently, SKOG showed significant (p < 0.01) anti-inflammatory activities as characterized by reducing the effects of xylene-induced increases of ear weight, thickness of total ear and ear dermis, and number of infiltrated inflammatory cells in the ear dermis, in a dose-dependent manner. These results supported that SKOG might have potential therapeutic effects to be used as an antitussive, expectorant, and anti-inflammatory agents in the prevention or treatment of chronic bronchitis and asthma. Full article
(This article belongs to the Special Issue Functional Food and Chronic Disease)
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Article
Analysis of Polygonal Vortex Flows in a Cylinder with a Rotating Bottom
Appl. Sci. 2021, 11(3), 1348; https://doi.org/10.3390/app11031348 - 02 Feb 2021
Viewed by 795
Abstract
The present paper provides a physically sound numerical modeling of liquid flows experimentally observed inside a vertical circular cylinder with a stationary envelope, rotating bottom and open top. In these flows, the resulting vortex depth may be such that the rotating bottom disk [...] Read more.
The present paper provides a physically sound numerical modeling of liquid flows experimentally observed inside a vertical circular cylinder with a stationary envelope, rotating bottom and open top. In these flows, the resulting vortex depth may be such that the rotating bottom disk becomes partially exposed, and rather peculiar polygon shapes appear. The parameters and features of this work are chosen based on a careful analysis of the literature. Accordingly, the cylinder inner radius is 145 mm and the initial water height is 60 mm. The experiments with bottom disk rotation frequencies of 3.0, 3.4, 4.0 and 4.6 Hz are simulated. The chosen frequency range encompasses the regions of ellipse and triangle shapes as observed in the experimental studies reported in the literature. The free surface flow is expected to be turbulent, with the Reynolds number of O(105). The Large Eddy Simulation (LES) is adopted as the numerical approach, with a localized dynamic Subgrid-Scale Stresses (SGS) model including an energy equation. Since the flow obviously requires a surface tracking or capturing method, a volume-of-fluid (VOF) approach has been chosen based on the findings, where this method provided stable shapes in the ranges of parameters found in the corresponding experiments. Expected ellipse and triangle shapes are revealed and analyzed. A detailed character of the numerical results allows for an in-depth discussion and analysis of the mechanisms and features which accompany the characteristic shapes and their alterations. As a result, a unique insight into the polygon flow structures is provided. Full article
(This article belongs to the Section Mechanical Engineering)
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Article
A Bacterial Chemotaxis-Inspired Coordination Strategy for Coverage and Aggregation of Swarm Robots
Appl. Sci. 2021, 11(3), 1347; https://doi.org/10.3390/app11031347 - 02 Feb 2021
Cited by 1 | Viewed by 697
Abstract
Many bio-inspired coordination strategies have been investigated for swarm robots. Bacterial chemotaxis exhibits a certain degree of intelligence, and has been developed some optimization algorithm for robot(s), e.g., bacterial foraging optimization algorithm (BFOA) and bacterial colony chemotaxis optimization algorithm (BCC). This paper proposes [...] Read more.
Many bio-inspired coordination strategies have been investigated for swarm robots. Bacterial chemotaxis exhibits a certain degree of intelligence, and has been developed some optimization algorithm for robot(s), e.g., bacterial foraging optimization algorithm (BFOA) and bacterial colony chemotaxis optimization algorithm (BCC). This paper proposes a bacterial chemotaxis-inspired coordination strategy (BCCS) of swarm robotic systems for coverage and aggregation. The coverage is the problem of finding a solution to uniformly deploy robots on a given bounded space. To solve this problem, this paper uses chaotic preprocessing to generate the initial positions of the robots. After the initialization, each robot calculates the area only covered by itself as the fitness function value. Then, each robot makes an action, running or rotating, depending on coordination strategy inspired bacterial chemotaxis. Moreover, we extend this solution and introduce a random factor to overcome aggregation, which is to guide robots to rendezvous at an unspecified point. The simulation results demonstrate the superior performance of the proposed coordination strategy in both success rate and an average number of iterations than other controllers. Full article
(This article belongs to the Section Robotics and Automation)
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Article
Effects of Black Jade on Osteogenic Differentiation of Adipose Derived Stem Cells under Benzopyrene
Appl. Sci. 2021, 11(3), 1346; https://doi.org/10.3390/app11031346 - 02 Feb 2021
Viewed by 818
Abstract
Jade, a popular gemstone symbolizing beauty, grace, and longevity, is known to improve blood circulation; however, scientific research evidence is still lacking. The effect of black jade extract on the expression levels of apoptotic and osteogenic genes was validated using qPCR and flow [...] Read more.
Jade, a popular gemstone symbolizing beauty, grace, and longevity, is known to improve blood circulation; however, scientific research evidence is still lacking. The effect of black jade extract on the expression levels of apoptotic and osteogenic genes was validated using qPCR and flow cytometry. In combination with the use of a fluorescence microscope, osteogenic differentiation and the stained osteocytes count were analyzed. Under the pressure of benzo(a)pyrene, dermal cell apoptosis was accelerated and the osteogenic differentiation of adipose-derived stem cells (ASCs) was suppressed; but black jade extract counteracted the effects. Through an anti-apoptotic mechanism, the extract suppressed the expression of apoptotic proteins Bax and cytochrome C to 9 and 4.8 times, respectively, compared to that in dermal cells exposed to benzo(a)pyrene. During osteogenic differentiation of ASCs, the extract enhanced their differentiation despite being exposed to benzo(a)pyrene, and the relative levels of the osteoblast differentiation markers osteoponin, osteocalcin, and sclerostin were 1.87, 2.54, and 3.9 times higher, respectively, than those in the conditioned medium by benzo(a)pyrene. These effects of the extract indicate that black jade extract is very useful when applied as a functional biomaterial. Full article
(This article belongs to the Section Applied Biosciences and Bioengineering)
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Article
Index of Body Inflammation for Maxillofacial Surgery Purpose-to Make the Soluble Urokinase-Type Plasminogen Activator Receptor Serum Level Independent on Patient Age
Appl. Sci. 2021, 11(3), 1345; https://doi.org/10.3390/app11031345 - 02 Feb 2021
Cited by 2 | Viewed by 607
Abstract
Background: The serum suPAR level is affected in humans by it increases with age. Therefore it makes difficult interpretation and any comparison of age varied groups. The aim of this study is to find simple way to age independent presentation of suPAR serum [...] Read more.
Background: The serum suPAR level is affected in humans by it increases with age. Therefore it makes difficult interpretation and any comparison of age varied groups. The aim of this study is to find simple way to age independent presentation of suPAR serum level for maxillofacial surgery purpose. Methods: In generally healthy patients from 15 to 59 y.o. suPAR level was tested in serum before orthognathic or minor traumatologic procedures. Five ways to make the suPAR serum level assessment independent of age are proposed. Results: One way of making suPAR levels independent of age led to the result with the same statistical distribution as in the raw suPAR serum material and this distribution is the normal. Conclusion: The simple way for suPAR serum level analysis without its dependence on patient age is calculation of the index of body inflammation understood as square root of squared suPAR serum level divided by logarithm of patient age to base 10. Full article
(This article belongs to the Special Issue Current Challenges of Oral and Maxillofacial Surgery)
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Article
Anomalous Event Recognition in Videos Based on Joint Learning of Motion and Appearance with Multiple Ranking Measures
Appl. Sci. 2021, 11(3), 1344; https://doi.org/10.3390/app11031344 - 02 Feb 2021
Cited by 2 | Viewed by 898
Abstract
Given the scarcity of annotated datasets, learning the context-dependency of anomalous events as well as mitigating false alarms represent challenges in the task of anomalous activity detection. We propose a framework, Deep-network with Multiple Ranking Measures (DMRMs), which addresses context-dependency using a joint [...] Read more.
Given the scarcity of annotated datasets, learning the context-dependency of anomalous events as well as mitigating false alarms represent challenges in the task of anomalous activity detection. We propose a framework, Deep-network with Multiple Ranking Measures (DMRMs), which addresses context-dependency using a joint learning technique for motion and appearance features. In DMRMs, the spatial-time-dependent features are extracted from a video using a 3D residual network (ResNet), and deep motion features are extracted by integrating the motion flow maps’ information with the 3D ResNet. Afterward, the extracted features are fused for joint learning. This data fusion is then passed through a deep neural network for deep multiple instance learning (DMIL) to learn the context-dependency in a weakly-supervised manner using the proposed multiple ranking measures (MRMs). These MRMs consider multiple measures of false alarms, and the network is trained with both normal and anomalous events, thus lowering the false alarm rate. Meanwhile, in the inference phase, the network predicts each frame’s abnormality score along with the localization of moving objects using motion flow maps. A higher abnormality score indicates the presence of an anomalous event. Experimental results on two recent and challenging datasets demonstrate that our proposed framework improves the area under the curve (AUC) score by 6.5% compared to the state-of-the-art method on the UCF-Crime dataset and shows AUC of 68.5% on the ShanghaiTech dataset. Full article
(This article belongs to the Special Issue Computing and Artificial Intelligence for Visual Data Analysis)
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Article
The Usage of the Harmony Search Algorithm for the Optimal Design Problem of Reinforced Concrete Retaining Walls
Appl. Sci. 2021, 11(3), 1343; https://doi.org/10.3390/app11031343 - 02 Feb 2021
Cited by 1 | Viewed by 1055
Abstract
In this paper, the Harmony Search (HS) algorithm is utilized to perform single and multivariate parametric studies to acquire the optimization of both size and cost of reinforced concrete (RC) retaining walls embedded in pure frictional soils. The geotechnical properties of the backfill [...] Read more.
In this paper, the Harmony Search (HS) algorithm is utilized to perform single and multivariate parametric studies to acquire the optimization of both size and cost of reinforced concrete (RC) retaining walls embedded in pure frictional soils. The geotechnical properties of the backfill and foundation soil such as shear strength angle, unit weight, and the ultimate bearing pressure of the soil have been used to create different cases for evaluating the effects of site properties on the size and cost of the wall. The change of depth of excavation and surcharge loading condition is fictionalized for generating different environmental conditions for all envisaged soil profiles to predict possible rates of influences. The unit cost of the concrete has also been evaluated as a variant to show the economic constraints on the selection of structural materials. The results of the analyses represent the integrated influences of different significant parameters on the achievement of minimum cost-dimension optimization. Besides, a well-known commercial geotechnical engineering software is used to compare the appropriateness of the suggested designs in terms of both the attainment of geotechnical stability and the structural requirements. Consequently, this study can guide both researchers and designers to select the proper and optimal sections of RC-retaining wall systems with simultaneous analyses of parameters that are influenced by the design process. Furthermore, the optimization results indicate that a significant cost reduction may be achieved when compared with the traditional pre-design method. Full article
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Article
Buckling of Rectangular Composite Pipes under Torsion
Appl. Sci. 2021, 11(3), 1342; https://doi.org/10.3390/app11031342 - 02 Feb 2021
Cited by 1 | Viewed by 610
Abstract
The numerical buckling load of rectangular composite pipes under torsional load was derived by using the energy method. The authors found no available simple design method or chart for the buckling loads of rectangular composite pipes, which are often used airplanes, spacecraft, and [...] Read more.
The numerical buckling load of rectangular composite pipes under torsional load was derived by using the energy method. The authors found no available simple design method or chart for the buckling loads of rectangular composite pipes, which are often used airplanes, spacecraft, and other lightweight structures, through their involvement in a Mars exploration airplane project. Thus, numerical results were obtained for length-to-width ratios (l/b) from 1 to 20, width-to-height ratios (h/b) from 1 to 6, and [0/90] layer ratios (r) from 0 to 1, which means [(0/90)r,(±45)1-r]s. The layups were assumed to be symmetric, and tension-bending, torsion-bending, and tension-shear coupling stiffnesses were ignored. To establish a simple design method, a closed-form polynomial equation for the buckling load factor was derived by minimizing the weighted residuals of the safe and non-safe side errors, which were obtained by comparing the derived numerical results with the polynomial equations. As a result, the errors of the polynomial equation for the buckling load factor were 4.95% for the non-safe side and 12.4% for the safe side. The errors are sufficiently good for preliminary design use and for parametric design studies and optimization. Full article
(This article belongs to the Special Issue Selected Papers from IMETI 2020)
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Article
Non-Invasive Testing of Physical Systems Using Topological Sensitivity
Appl. Sci. 2021, 11(3), 1341; https://doi.org/10.3390/app11031341 - 02 Feb 2021
Viewed by 679
Abstract
A review of available results on non-destructive testing of physical systems, using the concept of topological sensitivity, is presented. This mathematical tool estimates the sensitivity of a set of measurements in some given sensors, distributed along the system, to defects/flaws that produce a [...] Read more.
A review of available results on non-destructive testing of physical systems, using the concept of topological sensitivity, is presented. This mathematical tool estimates the sensitivity of a set of measurements in some given sensors, distributed along the system, to defects/flaws that produce a degradation of the system. Such degradation manifests itself on the properties of the system. The good performance of this general purpose post-processing method is reviewed and illustrated in some applications involving non-destructive testing. These applications include structural health monitoring, considering both elastodynamic ultrasonic guided Lamb waves and active infrared thermography. Related methods can also be used in other fields, such as diagnosis/prognosis of engineering devices, which is also considered. Full article
(This article belongs to the Special Issue Nondestructive Testing (NDT): Volume II)
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Article
Simulink Model of a Thermoelectric Generator for Vehicle Waste Heat Recovery
Appl. Sci. 2021, 11(3), 1340; https://doi.org/10.3390/app11031340 - 02 Feb 2021
Cited by 4 | Viewed by 832
Abstract
More than 50% of the energy released through combustion in the internal combustion engine (ICE) is rejected to the environment. Recovering only a part of this energy can significantly improve the overall use of resources and the economic efficiency of road transport. One [...] Read more.
More than 50% of the energy released through combustion in the internal combustion engine (ICE) is rejected to the environment. Recovering only a part of this energy can significantly improve the overall use of resources and the economic efficiency of road transport. One solution to recoup a part of this otherwise wasted thermal energy is to use thermoelectric generator (TEG) modules for the conversion of heat directly into electricity. To aid in development of this technology, this effort covers the derivation of a respectively simple steady-state Simulink model that can be utilized to estimate and optimize TEG system performance for ICEs. The model was validated against experimental data found in literature utilizing water cooling for the cold side. Overall, relatively good agreement was found with the maximum error in generated power around 10%. Following, it was investigated whether air can be used as a cooling medium. It was established that, at the same temperature as the water (18.4 °C), a flow velocity of 13.1 m/s (or 47.2 km/h) is required to achieve a similar cold junction temperature and power output. Subsequently using the model with air cooling, the performance of a TEG installed on a heavy-duty vehicle traveling at 50, 80, 90, and 120 km/h under different ambient temperatures was analyzed. It was determined that both a lower temperature and a higher flow velocity can improve power output. A further increase of the power output requires a larger temperature gradient across the module, which can be achieved by a higher heat input on the hot side. Full article
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Article
Hexapod Robot Gait Switching for Energy Consumption and Cost of Transport Management Using Heuristic Algorithms
Appl. Sci. 2021, 11(3), 1339; https://doi.org/10.3390/app11031339 - 02 Feb 2021
Cited by 5 | Viewed by 1086
Abstract
Due to the prospect of using walking robots in an impassable environment for tracked or wheeled vehicles, walking locomotion is one of the most remarkable accomplishments in robotic history. Walking robots, however, are still being deeply researched and created. Locomotion over irregular terrain [...] Read more.
Due to the prospect of using walking robots in an impassable environment for tracked or wheeled vehicles, walking locomotion is one of the most remarkable accomplishments in robotic history. Walking robots, however, are still being deeply researched and created. Locomotion over irregular terrain and energy consumption are among the major problems. Walking robots require many actuators to cross different terrains, leading to substantial consumption of energy. A robot must be carefully designed to solve this problem, and movement parameters must be correctly chosen. We present a minimization of the hexapod robot’s energy consumption in this paper. Secondly, we investigate the reliance on power consumption in robot movement speed and gaits along with the Cost of Transport (CoT). To perform optimization of the hexapod robot energy consumption, we propose two algorithms. The heuristic algorithm performs gait switching based on the current speed of the robot to ensure minimum energy consumption. The Red Fox Optimization (RFO) algorithm performs a nature-inspired search of robot gait variable space to minimize CoT as a target function. The algorithms are tested to assess the efficiency of the hexapod robot walking through real-life experiments. We show that it is possible to save approximately 7.7–21% by choosing proper gaits at certain speeds. Finally, we demonstrate that our hexapod robot is one of the most energy-efficient hexapods by comparing the CoT values of various walking robots. Full article
(This article belongs to the Special Issue Modelling and Control of Mechatronic and Robotic Systems)
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Article
Multidimensional Emotion Recognition Based on Semantic Analysis of Biomedical EEG Signal for Knowledge Discovery in Psychological Healthcare
Appl. Sci. 2021, 11(3), 1338; https://doi.org/10.3390/app11031338 - 02 Feb 2021
Cited by 3 | Viewed by 855
Abstract
Electroencephalogram (EEG) as biomedical signal is widely applied in the medical field such as the detection of Alzheimer’s disease, Parkinson’s disease, etc. Moreover, by analyzing the EEG-based emotions, the mental status of individual can be revealed for further analysis on the psychological causes [...] Read more.
Electroencephalogram (EEG) as biomedical signal is widely applied in the medical field such as the detection of Alzheimer’s disease, Parkinson’s disease, etc. Moreover, by analyzing the EEG-based emotions, the mental status of individual can be revealed for further analysis on the psychological causes of some diseases such as cancer, which is considered as a vital factor on the induction of certain diseases. Therefore, once the emotional status can be correctly analyzed based on EEG signal, more healthcare-oriented applications can be furtherly carried out. Currently, in order to achieve efficiency and accuracy, diverse amounts of EEG-based emotions recognition methods generally extract features by analyzing the overall characteristics of signal, along with optimization strategy of channel selection to minimize the information redundancy. Those methods have been proved their effectiveness, however, there still remains a big challenge when applied with single channel information for emotion recognition task. Therefore, in order to recognize multidimensional emotions based on single channel information, an emotion quantification analysis (EQA) method is proposed to objectively analyze the semantically similarity between emotions in valence-arousal domains, and a multidimensional emotion recognition (EMER) model is proposed on recognizing multidimensional emotions according to the partial fluctuation pattern (PFP) features based on single channel information, and result shows that even though semantically similar emotions are proved to have similar change patterns in EEG signals, each single channel of 4 frequency bands can efficiently recognize 20 different emotions with an average accuracy above 93% separately. Full article
(This article belongs to the Special Issue Data Technology Applications in Life, Diseases, and Health)
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Article
Different Gymnastic Balls Affect Postural Balance Rather Than Core-Muscle Activation: A Preliminary Study
Appl. Sci. 2021, 11(3), 1337; https://doi.org/10.3390/app11031337 - 02 Feb 2021
Viewed by 827
Abstract
Background: In proprioceptive training, unstable devices produce multidirectional perturbations that must be counterbalanced by the postural control systems and core-muscle activation. We investigated whether different sizes and shapes of three gymnastic balls could affect core-muscle activation and postural balance when performing the same [...] Read more.
Background: In proprioceptive training, unstable devices produce multidirectional perturbations that must be counterbalanced by the postural control systems and core-muscle activation. We investigated whether different sizes and shapes of three gymnastic balls could affect core-muscle activation and postural balance when performing the same exercise. Methods: Eleven young healthy subjects were assessed on the balls, assuming two body postures (bipedal seated and unipedal seated) and performing a dynamic exercise. Two balls were spherical with different diameters, and one was ovoid. Postural balance and muscle activation were assessed through center of pressure (CoP)-related parameters and surface electromyography. Results: Statistical analysis showed a significant effect of the gymnastic balls (p < 0.001) and the body postures (p < 0.001) for the CoP-related parameters, with the ovoid shape and the bipedal sitting representing the easiest conditions. Core-muscle activation was affected only by body postures, with a higher activation in the unipedal sitting (p < 0.01). In the dynamic exercise, significant differences were only detected for the CoP-related parameters (p < 0.001). Conclusions: The shapes and sizes of the gymnastic balls produced different degrees of destabilization under the same body posture but left the core-muscle activation unaltered. In the dynamic exercise, the conformation of the balls did not represent the main determinant in producing destabilizing effects. Full article
(This article belongs to the Special Issue Biomechanical Spectrum of Human Sport Performance Ⅱ)
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Article
Leveraging the Advantages of Additive Manufacturing to Produce Advanced Hybrid Composite Structures for Marine Energy Systems
Appl. Sci. 2021, 11(3), 1336; https://doi.org/10.3390/app11031336 - 02 Feb 2021
Cited by 1 | Viewed by 961
Abstract
Many marine energy systems designers and developers are beginning to implement composite materials into the load-bearing structures of their devices, but traditional mold-making costs for composite prototyping are disproportionately high and lead times can be long. Furthermore, established molding techniques for marine energy [...] Read more.
Many marine energy systems designers and developers are beginning to implement composite materials into the load-bearing structures of their devices, but traditional mold-making costs for composite prototyping are disproportionately high and lead times can be long. Furthermore, established molding techniques for marine energy structures generally require many manufacturing steps, such as secondary bonding and tooling. This research explores the possibilities of additively manufactured internal composite molds and how they can be used to reduce costs and lead times through novel design features and processes for marine energy composite structures. In this approach, not only can the composite mold be additively manufactured but it can also serve as part of the final load-bearing structure. We developed a conceptual design and implemented it to produce a reduced-scale additive/composite tidal turbine blade section to fully demonstrate the manufacturing possibilities. The manufacturing was successful and identified several critical features that could expedite the tidal turbine blade manufacturing process, such as single-piece construction, an integrated shear web, and embedded root fasteners. The hands-on manufacturing also helped identify key areas for continued research to allow for efficient, durable, and low-cost additive/composite-manufactured structures for future marine energy systems. Full article
(This article belongs to the Special Issue Design for Additive Manufacturing: Methods and Tools)
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Article
Evaluating the Real-World NOx Emission from a China VI Heavy-Duty Diesel Vehicle
by and
Appl. Sci. 2021, 11(3), 1335; https://doi.org/10.3390/app11031335 - 02 Feb 2021
Cited by 2 | Viewed by 678
Abstract
The manufacturers of China VI heavy-duty vehicles were required to conduct in-service conformity (ISC) tests by using a portable emissions measurement system (PEMS). The moving averaging window (MAW) method was used to evaluate the NOx emission required by the China VI emission standard. [...] Read more.
The manufacturers of China VI heavy-duty vehicles were required to conduct in-service conformity (ISC) tests by using a portable emissions measurement system (PEMS). The moving averaging window (MAW) method was used to evaluate the NOx emission required by the China VI emission standard. This paper presented the results of four PEMS tests of a China VI (step B) N3 category vehicle. Our analyses revealed that the real NOx emission of the test route was much higher than the result evaluated by the MAW method. We also found the data produced during the urban section of a PEMS test was completely excluded from the evaluation based on the current required boundary conditions. Therefore, in order to ensure the objectivity of the evaluation, this paper proposed three different evaluation methods. Method 1 merely set the power threshold as 10% for valid MAWs; Method 2 reclassified the MAWs into “Urban MAWs”, “Rural MAWs” and “Motorway MAWs” according to the vehicle speed. Method 3 reclassified the MAWs into “Hot MAWs” and “Cold MAWs” according to engine coolant temperature. The NOx emission evaluation results for Method 1 were not satisfactory, but those for Method 2 and Method 3 were close to the real NOx emission, the errors were all within ±10%. Full article
(This article belongs to the Special Issue Advances in Air Quality Monitoring and Assessment)
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Review
Passive Control of Base Pressure: A Review
Appl. Sci. 2021, 11(3), 1334; https://doi.org/10.3390/app11031334 - 02 Feb 2021
Cited by 1 | Viewed by 750
Abstract
In the present world, passive control finds application in various areas like flow over blunt projectiles, missiles, supersonic parallel diffusers (for cruise correction), the engine of jets, static testbeds of rockets, the ports of internal combustion engines, vernier rockets, and single expansion ramp [...] Read more.
In the present world, passive control finds application in various areas like flow over blunt projectiles, missiles, supersonic parallel diffusers (for cruise correction), the engine of jets, static testbeds of rockets, the ports of internal combustion engines, vernier rockets, and single expansion ramp nozzle (SERN) rockets. In this review, various passive control techniques to control the base pressure and regulate the drag force are discussed. In the study, papers ranging from subsonic, sonic, and supersonic flow are discussed. Different types of passive control management techniques like cavity, ribs, dimple, static cylinder, spikes, etc., are discussed in this review article. This study found that the passive control device can control the base pressure, resulting in an enhancement in the base pressure and reducing the base drag. Also, passive control is very efficient whenever there is a favorable pressure gradient at the nozzle exit. Full article
(This article belongs to the Special Issue New Trends in Applied Aerodynamics)
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Article
Development of a Maintenance and Spare Parts Distribution Model for Increasing Aircraft Efficiency
Appl. Sci. 2021, 11(3), 1333; https://doi.org/10.3390/app11031333 - 02 Feb 2021
Cited by 2 | Viewed by 981
Abstract
Maintenance management plays a key role in many industries, as maintenance determines the availability of systems, influences their lifespan, impacts customer satisfaction, and as a result affects overall investment profitability. In this context, the aviation industry seeks models to improve efficiency. Researchers seek [...] Read more.
Maintenance management plays a key role in many industries, as maintenance determines the availability of systems, influences their lifespan, impacts customer satisfaction, and as a result affects overall investment profitability. In this context, the aviation industry seeks models to improve efficiency. Researchers seek to provide conceptual models that help to shape the industry’s operations. Spare parts management plays a fundamental role in aviation, considering the predominance of planned maintenance. In this study, we analyzed the impact of the distribution network design for spare parts management and the fixed and dynamic planned maintenance intervals on the overall efficiency of an aircraft fleet. We present a conceptual model considering a variety of topics, such as distribution network design, that have been managed to a limited extent based on maintenance management. A simulation model was developed by applying the conceptual model for the aviation industry considering an aircraft fleet over its whole life cycle. The simulation model provides results concerning the impact of the distribution network, maintenance intervals, and other key factors on the efficiency of the aircraft fleet. The simulation enables a comparison of different distribution networks and maintenance strategies to decide which of them is the best fit for each spare part. The approach we propose enables companies and managers to make decisions informed by a centralized tool with all the relevant factors concerning the maintenance management of an aircraft fleet over its life cycle. As a result, managers are provided with a conceptual and simulation model for the assessment of future what-if scenarios based on aggregated databases from multiple sources without delays and with a dynamic vision of the relevant relationships between factors. Full article
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Article
Improving the Accuracy of Analytical Relationships for Mechanical Properties of Permeable Metamaterials
Appl. Sci. 2021, 11(3), 1332; https://doi.org/10.3390/app11031332 - 02 Feb 2021
Cited by 4 | Viewed by 943
Abstract
Permeable porous implants must satisfy several physical and biological requirements in order to be promising materials for orthopaedic application: they should have the proper levels of stiffness, permeability, and fatigue resistance approximately matching the corresponding levels in bone tissues. This can be achieved [...] Read more.
Permeable porous implants must satisfy several physical and biological requirements in order to be promising materials for orthopaedic application: they should have the proper levels of stiffness, permeability, and fatigue resistance approximately matching the corresponding levels in bone tissues. This can be achieved using designer materials, which exhibit exotic properties, commonly known as metamaterials. In recent years, several experimental, numerical, and analytical studies have been carried out on the influence of unit cell micro-architecture on the mechanical and physical properties of metamaterials. Even though experimental and numerical approaches can study and predict the behaviour of different micro-structures effectively, they lack the ease and quickness provided by analytical relationships in predicting the answer. Although it is well known that Timoshenko beam theory is much more accurate in predicting the deformation of a beam (and as a result lattice structures), many of the already-existing relationships in the literature have been derived based on Euler–Bernoulli beam theory. The question that arises here is whether or not there exists a convenient way to convert the already-existing analytical relationships based on Euler–Bernoulli theory to relationships based on Timoshenko beam theory without the need to rewrite all the derivations from the start point. In this paper, this question is addressed and answered, and a handy and easy-to-use approach is presented. This technique is applied to six unit cell types (body-centred cubic (BCC), hexagonal packing, rhombicuboctahedron, diamond, truncated cube, and truncated octahedron) for which Euler–Bernoulli analytical relationships already exist in the literature while Timoshenko theory-based relationships could not be found. The results of this study demonstrated that converting analytical relationships based on Euler–Bernoulli to equivalent Timoshenko ones can decrease the difference between the analytical and numerical values for one order of magnitude, which is a significant improvement in accuracy of the analytical formulas. The methodology presented in this study is not only beneficial for improving the already-existing analytical relationships, but it also facilitates derivation of accurate analytical relationships for other, yet unexplored, unit cell types. Full article
(This article belongs to the Special Issue Acoustic Metamaterials and Acoustic Foams: Recent Advances)
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Article
Multiple Narrowband Interferences Characterization, Detection and Mitigation Using Simplified Welch Algorithm and Notch Filtering
Appl. Sci. 2021, 11(3), 1331; https://doi.org/10.3390/app11031331 - 02 Feb 2021
Viewed by 650
Abstract
By increasing the demand for radio frequency (RF) and access of hackers and spoofers to low price hardware and software defined radios (SDR), radio frequency interference (RFI) became a more frequent and serious problem. In order to increase the security of satellite communication [...] Read more.
By increasing the demand for radio frequency (RF) and access of hackers and spoofers to low price hardware and software defined radios (SDR), radio frequency interference (RFI) became a more frequent and serious problem. In order to increase the security of satellite communication (Satcom) and guarantee the quality of service (QoS) of end users, it is crucial to detect the RFI in the desired bandwidth and protect the receiver with a proper mitigation mechanism. Digital narrowband signals are so sensitive into the interference and because of their special power spectrum shape, it is hard to detect and eliminate the RFI from their bandwidth. Thus, a proper detector requires a high precision and smooth estimation of input signal power spectral density (PSD). By utilizing the presented power spectrum by the simplified Welch method, this article proposes a solid and effective algorithm that can find all necessary interference parameters in the frequency domain while targeting practical implantation for the embedded system with minimum complexity. The proposed detector can detect several multi narrowband interferences and estimate their center frequency, bandwidth, power, start, and end of each interference individually. To remove multiple interferences, a chain of several infinite impulse response (IIR) notch filters with multiplexers is proposed. To minimize damage to the original signal, the bandwidth of each notch is adjusted in a way that maximizes the received signal to noise ratio (SNR) by the receiver. Multiple carrier wave interferences (MCWI) is utilized as a jamming attack to the Digital Video Broadcasting-Satellite-Second Generation (DVB-S2) receiver and performance of a new detector and mitigation system is investigated and validated in both simulation and practical tests. Based on the obtained results, the proposed detector can detect a weak power interference down to −25 dB and track a hopping frequency interference with center frequency variation speed up to 3 kHz. Bit error ratio (BER) performance shows 3 dB improvement by utilizing new adaptive mitigation scenario compared to non-adaptive one. Finally, the protected DVB-S2 can receive the data with SNR close to the normal situation while it is under the attack of the MCWI jammer. Full article
(This article belongs to the Section Electrical, Electronics and Communications Engineering)
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Article
Volatile Organic Compounds in Breads Prepared with Different Sourdoughs
Appl. Sci. 2021, 11(3), 1330; https://doi.org/10.3390/app11031330 - 02 Feb 2021
Cited by 4 | Viewed by 710
Abstract
Sourdough is an old example of a natural starter composed of a mixture of flour, water, and metabolites and is produced by naturally occurring lactic acid bacteria and yeasts that influence bread aroma. In this work, four types of sourdough were used to [...] Read more.
Sourdough is an old example of a natural starter composed of a mixture of flour, water, and metabolites and is produced by naturally occurring lactic acid bacteria and yeasts that influence bread aroma. In this work, four types of sourdough were used to prepare bread: one sourdough with yeast beer and three with bacteria and yeasts. The physicochemical parameters (pH, moisture, water activity, and organic acids) of the bread and sourdoughs were assessed. Lactic, acetic, and succinic acids were found in considerable amounts in sourdoughs and the corresponding breads. The fermentation quotient (molar ratio between lactic and acetic acid) ranged from 0.39 to 3.4 in sourdoughs. Lactic acid was prevalent in all types of bread and showed the highest value in bread made from sourdough with a 1.5 bacteria/yeast ratio (8722.24 mg/kg). Moreover, volatile organic compounds were identified in bread samples. Alcohols, aldehydes, and acetic acid were mainly found. The alcohol concentration ranged from 140.88 to 401.20 ng/g. Aldehydes ranged from 185.01 to 454.95 ng/g, and acetic acid ranged from 91.40 to 173.81 ng/g. Bread prepared from sourdough with a 1.5 bacteria/yeast ratio showed a considerable amount of alcohols and acetic acid. Full article
(This article belongs to the Special Issue Advances in Food Flavor Analysis)
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Article
Chaos-Based Synchronized Dynamic Keys and Their Application to Image Encryption with an Improved AES Algorithm
Appl. Sci. 2021, 11(3), 1329; https://doi.org/10.3390/app11031329 - 02 Feb 2021
Cited by 5 | Viewed by 953
Abstract
This study aimed to design chaos-based synchronized dynamic keys and develop an improved chaos-based advanced encryption standard (AES) algorithm with the proposed synchronized random keys. First, based on sliding mode control (SMC) technology, a rippling control scheme was introduced to guarantee the synchronization [...] Read more.
This study aimed to design chaos-based synchronized dynamic keys and develop an improved chaos-based advanced encryption standard (AES) algorithm with the proposed synchronized random keys. First, based on sliding mode control (SMC) technology, a rippling control scheme was introduced to guarantee the synchronization between master–slave discrete chaotic systems. Under the synchronization, the same dynamic random chaos signals could be simultaneously obtained at the transmitter and receiver in communication systems. Then, a novel modified AES cryptosystem with dynamic random keys based on chaos synchronization was presented. In a traditional AES cryptosystem, a static key is used, and it must be exchanged in advance and confirmed to be safely kept. However, in the proposed design, by introducing the synchronization technology of chaotic systems, the static key becomes dynamic and random, and it does not need to be kept or transmitted in open channels. Consequently, the disadvantage of key storage could be eliminated and the security of encryption could be improved. Finally, the developed chaos-based AES (CAES) algorithm has been applied to construct a novel image encryption algorithm. The statistical analysis, histogram, information entropy, and correlation indexes have been calculated and analyzed through simulation experiments in order to demonstrate the capability and improvement of this presented CAES cryptosystem. Full article
(This article belongs to the Special Issue Physics and Mechanics of New Materials and Their Applications 2020)
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Article
Full-Closed-Loop Time-Domain Integrated Modeling Method of Optical Satellite Flywheel Micro-Vibration
Appl. Sci. 2021, 11(3), 1328; https://doi.org/10.3390/app11031328 - 02 Feb 2021
Cited by 1 | Viewed by 669
Abstract
Due to the micro-vibration of flywheels, the imaging quality of a high-resolution optical remote sensing satellite will be deteriorated, and the micro-vibration effect on the payload is complicated, so it is essential to establish a reasonable and accurate theoretical simulation model for it. [...] Read more.
Due to the micro-vibration of flywheels, the imaging quality of a high-resolution optical remote sensing satellite will be deteriorated, and the micro-vibration effect on the payload is complicated, so it is essential to establish a reasonable and accurate theoretical simulation model for it. This paper presents a method of full-closed-loop time-domain integrated modeling to estimate the impacts of micro-vibration generated by flywheels on optical satellites. The method consists of three parts. First, according to the satellites’ micro-vibration influence mechanism in orbit, this paper establishes a full-closed-loop model framework. The overall model input is the instructions received and the output is the image shift. Second, in order to meet the requirements of time-domain simulation, this paper proposes a time-domain vibration source subsystem model in the form of cosine harmonic superposition, and it integrates vibration source, structural, control, and optical subsystem models to create a full-closed-loop time-domain analysis model that can obtain the responses of micro-vibration in time and frequency domains. Lastly, the author designs a ground experiment and compares simulation results with experiment results. Compared with the ground experiment, frequency error is less than 0.4% at typical responses. Although the amplitude error is large at some typical responses, the mean root square error is less than 35%. Based on the data, the proposed integrated modeling method can be considered as an accurate methodology to predict the impacts of micro-vibration. Full article
(This article belongs to the Section Aerospace Science and Engineering)
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Article
A Novel Automatic Modulation Classification Method Using Attention Mechanism and Hybrid Parallel Neural Network
Appl. Sci. 2021, 11(3), 1327; https://doi.org/10.3390/app11031327 - 02 Feb 2021
Cited by 5 | Viewed by 884
Abstract
Automatic Modulation Classification (AMC) is of paramount importance in wireless communication systems. Existing methods usually adopt a single category of neural network or stack different categories of networks in series, and rarely extract different types of features simultaneously in a proper way. When [...] Read more.
Automatic Modulation Classification (AMC) is of paramount importance in wireless communication systems. Existing methods usually adopt a single category of neural network or stack different categories of networks in series, and rarely extract different types of features simultaneously in a proper way. When it comes to the output layer, softmax function is applied for classification to expand the inter-class distance. In this paper, we propose a hybrid parallel network for the AMC problem. Our proposed method designs a hybrid parallel structure which utilizes Convolution Neural Network (CNN) and Gate Rate Unit (GRU) to extract spatial features and temporal features respectively. Instead of superposing these two categories of features directly, three different attention mechanisms are applied to assign weights for different types of features. Finally, a cosine similarity metric named Additive Margin softmax function, which can expand the inter-class distance and compress the intra-class distance simultaneously, is adopted for output. Simulation results demonstrate that the proposed method can achieve remarkable performance on an open access dataset. Full article
(This article belongs to the Special Issue Advances in Intelligent Internet of Things Ⅱ)
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Article
Influence of Post-Flowering Climate Conditions on Anthocyanin Profile of Strawberry Cultivars Grown from North to South Europe
Appl. Sci. 2021, 11(3), 1326; https://doi.org/10.3390/app11031326 - 02 Feb 2021
Cited by 5 | Viewed by 979
Abstract
The effect of cultivar and environmental variations and their interaction on anthocyanin components of strawberry were assessed for six cultivars grown in five locations from North to South of Europe in two different years. To evaluate the impact of latitude- and altitude-related factors, [...] Read more.
The effect of cultivar and environmental variations and their interaction on anthocyanin components of strawberry were assessed for six cultivars grown in five locations from North to South of Europe in two different years. To evaluate the impact of latitude- and altitude-related factors, daily mean (Tmean), maximum (Tmax) and minimum (Tmin) temperature and global radiation accumulated for 3, 5, 10 and 15 days before fruit sampling, was analyzed. In general, fruits grown in the south were more enriched in total anthocyanin and pelargonidin-3-glucoside (pel-3-glc), the most abundant anthocyanin in strawberry. Principal component analysis (PCA) provided a separation of the growing locations within a cultivar due to latitudinal climatic differences, temporary weather changes before fruit collection and cultivation technique. PCA also depicted different patterns for anthocyanin distribution indicating a cultivar specific reaction on the environmental factors. The linear regression analysis showed that pel-3-glc was relatively less affected by these factors, while the minor anthocyanins cyanidin-3-glucoside, cyanidin-3-(6-O-malonyl)-glucoside, pelargonidin-3-rutinoside and pelargonidin-3-(6-O-malonoyl)-glucoside were sensitive to Tmax. The global radiation strongly increased cya-3-mal-glc in ‘Frida’ and pel-3-rut in ‘Frida’ and ‘Florence’. ‘Candonga’ accumulated less pel-3-glc and total anthocyanin with increased global radiation. The anthocyanin profiles of ‘Gariguette’ and ‘Clery’ were unaffected by environmental conditions. Full article
(This article belongs to the Special Issue Potential Health Benefits of Fruits and Vegetables)
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Article
Parameters Identification of the Fractional-Order Permanent Magnet Synchronous Motor Models Using Chaotic Ensemble Particle Swarm Optimizer
Appl. Sci. 2021, 11(3), 1325; https://doi.org/10.3390/app11031325 - 02 Feb 2021
Cited by 1 | Viewed by 768
Abstract
In this paper, novel variants for the Ensemble Particle Swarm Optimizer (EPSO) are proposed where ten chaos maps are merged to enhance the EPSO’s performance by adaptively tuning its main parameters. The proposed Chaotic Ensemble Particle Swarm Optimizer variants (C.EPSO) are examined with [...] Read more.
In this paper, novel variants for the Ensemble Particle Swarm Optimizer (EPSO) are proposed where ten chaos maps are merged to enhance the EPSO’s performance by adaptively tuning its main parameters. The proposed Chaotic Ensemble Particle Swarm Optimizer variants (C.EPSO) are examined with complex nonlinear systems concerning equal order and variable-order fractional models of Permanent Magnet Synchronous Motor (PMSM). The proposed variants’ results are compared to that of its original version to recommend the most suitable variant for this non-linear optimization problem. A comparison between the introduced variants and the previously published algorithms proves the developed technique’s efficiency for further validation. The results emerge that the Chaotic Ensemble Particle Swarm variants with the Gauss/mouse map is the most proper variant for estimating the parameters of equal order and variable-order fractional PMSM models, as it achieves better accuracy, higher consistency, and faster convergence speed, it may lead to controlling the motor’s unwanted chaotic performance and protect it from ravage. Full article
(This article belongs to the Special Issue Modeling, Design and Control of Electric Machines)
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Article
Waste-to-Energy Process to Recover Dangerous Pollutants in an Environmental Protected Area
Appl. Sci. 2021, 11(3), 1324; https://doi.org/10.3390/app11031324 - 02 Feb 2021
Cited by 1 | Viewed by 601
Abstract
The present study aims to extract the polluting material from a lagoon and use it as an alternative fuel in cement industries. To this end, in the methodology will analyze two alternatives for the waste: fuel generation and incineration. The polluting material from [...] Read more.
The present study aims to extract the polluting material from a lagoon and use it as an alternative fuel in cement industries. To this end, in the methodology will analyze two alternatives for the waste: fuel generation and incineration. The polluting material from the Arganda lagoon has highly calorific value to be used as fuel. Thus, not only are these wastes used, but also an area with potentially hazardous waste is decontaminated. After the extraction, which due to the characteristics of the material is chosen for the novel pumping extraction, and subsequent generation of fuel, the process for using this waste is through the distribution of the created fuel to nine cement plants in Spain, leading to significant environmental benefits. The results of the process shows an energy efficiency of 97% for using the waste as fuel, and a consumed energy of approximately 6000 kWh/t·waste to the process that leads to the desired environmental benefit. The use of waste contributes to the reduction of CO2 emissions and a decrease in the use of fossil fuels. Full article
(This article belongs to the Section Environmental Sciences)
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Article
Cocrystal Prediction Using Machine Learning Models and Descriptors
Appl. Sci. 2021, 11(3), 1323; https://doi.org/10.3390/app11031323 - 01 Feb 2021
Cited by 1 | Viewed by 1348
Abstract
Cocrystals are of much interest in industrial application as well as academic research, and screening of suitable coformers for active pharmaceutical ingredients is the most crucial and challenging step in cocrystal development. Recently, machine learning techniques are attracting researchers in many fields including [...] Read more.
Cocrystals are of much interest in industrial application as well as academic research, and screening of suitable coformers for active pharmaceutical ingredients is the most crucial and challenging step in cocrystal development. Recently, machine learning techniques are attracting researchers in many fields including pharmaceutical research such as quantitative structure-activity/property relationship. In this paper, we develop machine learning models to predict cocrystal formation. We extract descriptor values from simplified molecular-input line-entry system (SMILES) of compounds and compare the machine learning models by experiments with our collected data of 1476 instances. As a result, we found that artificial neural network shows great potential as it has the best accuracy, sensitivity, and F1 score. We also found that the model achieved comparable performance with about half of the descriptors chosen by feature selection algorithms. We believe that this will contribute to faster and more accurate cocrystal development. Full article
(This article belongs to the Special Issue Applications of Artificial Intelligence in Pharmaceutics)
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Article
Attenuation of DC-Link Pulsation of a Four-Wire Inverter during Phase Unbalanced Current Operation
Appl. Sci. 2021, 11(3), 1322; https://doi.org/10.3390/app11031322 - 01 Feb 2021
Cited by 1 | Viewed by 693
Abstract
This paper proposes a control algorithm for a hybrid power electronic AC/DC converter for prosumer applications operating under deep phase current asymmetry. The proposed system allows independent control of active and reactive power for each phase of the power converter without current pulsation [...] Read more.
This paper proposes a control algorithm for a hybrid power electronic AC/DC converter for prosumer applications operating under deep phase current asymmetry. The proposed system allows independent control of active and reactive power for each phase of the power converter without current pulsation on the DC link connected to an energy store. The system and its algorithm are based on a three-phase converter in four-wire topology (AC/DC 3p-4w) with two dual-active bridge (DC/DC) converters, interfaced with a supercapacitor and an energy storage. The control algorithm tests were carried out in a Hardware in the Loop environment. Obtained results indicate that operation with deep unbalances and powers of opposite signs in individual phases leads to current oscillations in the DC link. This phenomenon significantly limits energy storage utilization due to safety and durability reasons. The proposed algorithm significantly reduces the level of pulsation in the DC link which increases safety and reduces strain on lithium-ion storage technology, enabling their application in four-wire converter applications. Full article
(This article belongs to the Special Issue Power Electronics in Power Networks)
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